Commutators and other electric current collectors



Aug. 7, 1956 R. J. PERRY 2,758,229

COMMUTATORS AND OTHER ELECTRIC CURRENT COLLECTORS Filed Nov. 21, 1952COLLECTOR COMPRISING S/NTERED COPPR./IND OTHER MET/4L 0F LOWER CONDUCT[V] T) THAN COPPER I CARBON BRUSH CflRBO/V BRUSH I X INVENTOR512725245265 John Perify BY w /& ATTQRNEYS United States PatentCOMIMUTATORS AND OTHER ELECTRIC CURRENT COLLECTORS Reginald John Perry,Wallington, England, assignor to The Morgan Crucible Company Limited,London, England, a company of Great Britain Application November 21,1952, Serial No. 321,817

Claims priority, application Great Britain November 22, 1951 19 Claims.(Cl. 310-231) This invention relates to improvements in electric currentcollectors such, for example, as commutators and slip rings. Theinvention will be described herein with particular reference tocommutators but it is to be understood that the invention is applicablein like manner to electric current collectors of other types.

It has been known for some time that the brushes of dynamo-electricmachines on aircraft wear rapidly at high altitudes and that such brushwear has been so pronounced at altitudes of more than about 25,000 feetas to have presented a serious problem. Various attempts were made tosolve this problem and it was discovered that the wear resistanceproperties of brushes could be considerably improved by theincorporation in the brush of certain substances or so-called adjuvants.In particular, the adjuvants proposed have been salts and oxides ofalkaline earth metals, metal halides and sulphides, and metallic lead.

In the specification of the copending application Serial No. 298,470 animproved manufacture of brushes having resistance to wear at very highaltitudes has been described.

The basis of the present invention is the discovery that brushresistance to wear at high altitudes can be enhanced to a remarkabledegree by a departure from the ordinary method of manufacturing thecommutator upon which the brushes operate. Such commutators, and likecurrent collecting devices, used on aircraft are normally of small sizecompared with those used in electrical plant on larger vessels or on theground, and the invention is especially applicable to commutators andthe like which are relatively small.

According to the present invention, the current collecting portion of acommutator or like current collector is made from sintered copper inconjunction with other metal of substantially lower electricalconductivity than copper in an amount of at least 5% based on the weightof the whole. The practical upper limit for the amount of other metalmay be as high as about 40% or in some cases even higher. For instancenickel may be used in amounts up to 70%. Generally, the optimum amountis between and Particularly suitable as the other metal are lead, iron,chromium, nickel, tin and cadmium. These may be used individually, ortwo or more together, alloyed or otherwise.

The sintered body constituting the current collector according to theinvention may be produced in various ways. Generally the preferredmethod is to compact under pressure a mixture of fine powders of copperand the other metal or metals, and then to sinter the mixture at a hightemperature appropriate to the nature of the mixture.

Another method which is applicable when the other metal e. g. lead, hasa lower melting point than copper, is to introduce the other metal intoan already sintered body of copper by infiltration at a temperatureabove the melting point of the other metal but below the 2,758,229Patented Aug. 7, 1955 melting point of copper. Such infiltration may becarried out in a reducing atmosphere and may be facilitated by using avacuum to draw the molten metal into the pores of the sintered copperbody and/or by using pressure to force the molten metal into the pores.

A further method applicable in the case where the other metal or metalsis or are capable of alloying with copper, is to produce the alloy andthen to pulverize, compact and sinter it as such. The pulverizing isconveniently effected by solidifying an atomized spray of the moltenalloy.

In any of the aforesaid methods the mass to be sintered may contain asmall proportion, e. g. 1% by weight, of graphite. 1

The preferred amounts of the additional metal, in percentages of thetotal weight of the copper and the additional metal, are as follows:

If both iron and lead are used, the preferred percentage is 10% iron and20% lead, whilst it nickel and lead are used together the preferredpercentages are 20% nickel and 5% lead.

It will be appreciated that the sintered bodies produced according tothe invention may be commutator segments to be mounted in the customarymanner, or they may be complete commutator blanks which are subsequentlysplit, or they may be rings.

The particle size of the powder to be sintered is preferably such thatall the particles will pass through a sieve of meshes to a linear inch.A suitable pressure for compacting the powder is one of the order of 14tons per square inch. The sintering temperature will be dependent on thecomposition of the powder. In the case of a mixture of copper and iron,copper and chromium, or copper and nickel, a sintering temperature of800-1000 C. is suitable; for a mixture of copper and tin or copper andlead, or copper, iron and lead, or copper, nickel and lead, a sinteringtemperature of 700-850" C. is suitable; whilst for a mixture of copperand cadmium a sintering temperature of 400-600 C. is suitable.

I have found that a further improvement of the properties of the currentcollector made of a porous sintered body according to the invention isobtainable by impregnating the sintered body with an organic impregnantof a drying oil basis. Such organic impregnant may be of the nature of avarnish based on a drying oil which may contain a drier of the kindnormally used to accelerate and improve the hardening of drying oils, e.g. naphthenates of cobalt and other metals.

The term drying oil denotes any oil of animal or vegetable or syntheticorigin which will dry in air or harden or polymerize by heat. Examplesof vegetable oils are linseed oil and tung oil. Examples of other oilsare animal or fish oils which have been processed so as to be rendereddriable or hardenable either as such or in the presence of metal driers.Natural or synthetic resins may be included in the impregnant toincrease the hardness of the dried, oxidised or polymerized material.Examples of resin are wood rosin and copal resin. Examples of syntheticresins are those known as alkyd resins and these may be blended with thedrying oil or combined therewith as in the case of oil-modified alkydresins.

I am aware that it has been disclosed in United States specification No.2,053,662 to form commutator segments by compressing and sintering amixture of copper powders with certain other metal powders but in thatcase the object in view is the production of a material which is harderthan ordinary cold worked copper. The proportion of the added metalaccording to the said specification, for achieving the purpose disclosedtherein, is of the order of 3% or less, and the manufacture is such thatthe sintered mass is substantially nonporous.

In contradistinction, the present invention employs a higher proportionof added metal and the sintered mass may be porous. It would not appear,however, that the sintered metal structure is the basic reason for theimproved resistance to wear of brushes working on the commutator becausea commutator made of sintered copper alone does not produce theimprovement.

The single figure of the accompanying drawing schematically illustratesa representative embodiment of the invention.

I claim: 1

1. A rotatable electric current collector for dynamoelectric machinesused at high altitudes, said current collector having a peripheralcurrent collecting portion comprising copper and other conductive metalof substantially lower electrical conductivity than copper and from thegroup consisting of lead, iron, chromium, nickel, tin and cadmium and inan amount of at least percent based on the weight of the whole, whereincopper is sintered and carries said other metal.

2. A rotatable electric current collector for dynamoelectric machinesused at high altitudes, said current collector having a peripheralcurrent collecting portion comprising copper and other conductive metalof substantially lower electrical conductivity than copper and from thegroup consisting of lead, iron, chromium, nickel, tin and cadmium and inan amount between 10 percent and 30 percent based on the weight of thewhole, said current collecting portion being a sintered body of copperparticles having said other metal incorporated therein.

3. A rotatable electric current collector for dynamoelectric machinesusedat high altitudes, said current collector having a peripheralcurrent collecting portion comprising compacted copper and nickel in anamount between 10 percent and 70 percent based on the weight of thewhole, wherein said copper is sintered and carries said nickel.

4. A rotatable electric current collector for dynamoelectric machinesused at high altitudes, said current collector having a peripheralcurrent collecting portion cornprising copper and lead in an amountbetween 10 percent and 40 percent based on the weight of the whole, saidcurrent collecting portion being a sintered body of copper particleshaving said lead incorporated therein.

5. A rotatable electric current collector for dynamoelectric machinesused at high altitudes, said current collector having a peripheralcurrent collecting portion com prising copper and iron in an amountbetween 10 percent and 30 percent based on the weight of the whole, saidcurrent collecting portion being a sintered body of copper particleshaving said iron incorporated therein.

6. A rotatable electric current collector for dynamoelectric machinesused at high altitudes, said current collector having a peripheralcurrent collecting portion comprising compacted copper and chromium inan amount between 10 percent and 30 percent based on the Weight of thewhole, wherein said copper is sintered and carries said chromium.

7. A rotatable electric current collector for dynamoelectric machinesused at high altitudes, said current collector having a peripheralcurrent collecting portion comprising copper and tin in an amountbetween 10 percent and 30 percent based on the weight of the whole, saidcurrent collecting portion being a sintered body of copper particleshaving said tin incorporated therein.

8. A rotatable electric current collector for dynamo-- electric machinesused at high altitudes, said-current collector having a peripheralcurrent collecting portion comprising copper and cadmium in an amountbetween 10 percent and 25 percent based on the weight of the whole, saidcurrent collecting portion being a sintered body of copper particleshaving said cadmium incorporated therein.

9. A rotatable electric current collector for dynamoelectric machinesused at high altitudes, said current collector having a peripheralcurrent collecting portion comprising copper and at least one metal ofthe group consisting of lead, iron, chromium, nickel, tin and cadmium inan amount of at least 10 percent based on the weight of the whole,wherein said copper is sintered and carries at least one metal of saidgroup.

10. A rotatable electric current collector for dynamoelectric machinesused at high altitudes, said current collector having a peripheralcurrent collecting portion comprising copper and other conductive metalof substantially lower electrical conductivity than copper and from thegroup consisting of lead, iron, chromium, nickel, tin and cadmium and inan amount of at least 10 percent based on the weight of the whole, saidcurrent collecting portion consisting of a sintered mixture of copperpowder and powder of said other metal.

11. A rotatable electric current collector for dynamoelectric machinesused at high altitudes, said current collector having a peripheralcurrent collecting portion comprising copper, iron and lead, whereinsaid copper is sintered and carries iron and lead.

12. A rotatable electric current collector for dynamoelectric machinesused at high altitudes, said current collector having a peripheralcurrent collecting portion comprising copper, nickel and lead, saidcurrent collecting portion being a sintered body of copper particleshaving said nickel and lead incorporated therein.

13. A rotatable electric current collector for dynamoelectric machinesused at high altitudes, said current collector having a peripheralcurrent collecting portion comprising copper and other metal of lowermelting point than copper and of substantially lower electricalconductivity than copper and from the group consisting of lead, iron,

chromium, nickel, tin and cadmium and in an amount of at least 10percent based on the weight of the whole, said current collectingportion consisting of a sintered body of copper impregnated with saidmetal.

14. A rotatable electric current collector for dynamoelectric machinesused at high altitudes, said current collector having a peripheralcurrent collecting portion comprising copper and other metal of lowermelting point than copper and of substantially lower electricalconductivity than copper and from the group consisting of lead, iron,chromium, nickel, tin and cadmium and in an amount of at least 10percent based on the weight of the whole, wherein said currentcollecting portion consists of a sintered body of copper alloyed withsaid other metal. 157 A rotatable electric current collector fordynamoelectric machines used at high altitudes, said current collectorhaving a peripheral current collecting portion com prising copper andother metal of substantially lower electrical conductivity than copperand from the group consisting of lead, iron, chromium, nickel, tin andcadmium and in an amount of at least 10 percent based on the weight ofthe whole and impregnated with an organic impregnant of a drying oilbasis, said current collecting portion being a sintered body of copperparticles having said other metal incorporated therein.

16. A rotatable electric current collector for dynamoelectric machinesused at high altitudes, said current col lector having a peripheralcurrent collecting portion comprising copper and other metal ofsubstantially lower electrical conductivity than copper and from thegroup consisting of lead, iron, chromium, nickel, tin and cadmium and inan amount of at least 10 percent based on the weight of the whole andimpregnated with a varnish based on a drying oil, wherein said copper issintered and carries said other metal.

17. A rotatable electric current collector for dynamoelcctric machinesused at high altitudes, said current collector having a peripheralcurrent collecting portion comprising copper and other metal ofsubstantially lower electrical conductivity than copper and from thegroup consisting of lead, iron, chromium, nickel, tin and cadmium and inan amount of at least 10 percent based on the weight of the whole andimpregnated with a Varnish based on a drying oil and incorporating adrier, said current collecting portion being a sintered body of copperparticles having said other metal incorporated therein.

18. A rotatable electric current collector for dynamoelectric machinesused at high altitudes, said current collector having a peripheralcurrent collecting portion comprising copper and other conductive metalof substantially lower electrical conductivity than copper and from thegroup consisting of lead, iron, chromium, nickel, tin and cadmium and inan amount of at least 10 percent based on the weight of the whole andimpregnated with a varnish based on a drying oil and incorporatingresin, said current collecting portion being a sintered body of copperparticles having said other metal incorporated therein.

19. In a dynamo-electric machine for use at high altitudes thecombination of a carbon brush and a commutator having a compactedcurrent collecting portion comprising copper and other conductive metalof substan- 6 tially lower electrical conductivity than copper and fromthe group consisting of lead. iron, chromium, nickel, tin and cadmiumand in an amount of at least 10 percent based on the weight of theWhole, wherein said copper is sintered and carries said other metal.

References Cited in the file of this patent UNITED STATES PATENTS276,233 Edison Apr. 24, 1883 1,177,407 Gilson Mar. 28, 1916 1,248,924Sandell Dec. 4, 1917 1,937,465 Sherwood Nov. 28, 1933 2,053,662 HardySept. 8, 1936 2,075,444 Koehring Mar. 30, 1937 2,096,252 Koehring Oct.19, 1937 2,129,844 Kiefer Sept. 13, 1938 2,157,596 Davis May 9, 19392,182,741 Bolesky Dec. 5, 1939 2,362,007 Hensel Nov. 7, 1944 2,370,400Graves Feb. 27, 1945 2,376,706 Lum May 22, 1945 2,379,232 Hensel June26, 1945 FOREIGN PATENTS 101,993 Sweden July 8, 1941 456,018 GreatBritain Nov. 2, 1936

